As the quality of municipally supplied water has declined the consumer has maintained a desire for xe2x80x9cgood tastingxe2x80x9d water. The public has also become aware of the negative health effects associated with chlorination, used to disinfect tap water. Consumers seeking an alternative to tap water for better quality and taste have driven commercial xe2x80x9cBottled Waterxe2x80x9d sales to more than three billion dollars a year. A variety of filtration products have been introduced to compete with Bottled Water in providing these benefits, plus convenience and economy. The most popular of the filtration products has been the variety known as pour through carafes, or pitchers. While popular, the products presently marketed possess several drawbacks, that have kept the filters (treatment elements are all covered by the descriptor xe2x80x9cfilter(s)xe2x80x9d) from achieving greater favor. Major inadequacies have included the time element required to operate a pour through carafe. These devices must be cycled through filling a water chamber, generally comprising about half the volume of the overall container, and waiting until the water has trickled through the filtering element into a second, lower compartment occupying the second half of the container. The time required for filtration is typically 15-30 minutes for two to three liters of water. In addition, as only one-half of the container volume is usable, the containers are typically larger than fit conveniently within the refrigerator. Further, the quantity of treated water available is frequently less than needed, yet the time required to replenish (filter) the water is too long for the filter to be of practical value (i.e. fill a coffee pot etc.) if water had previously been withdrawn and not immediately refilled.
The drawbacks of filtration pitchers and carafes have been overcome by the invention herein disclosed, without diminishing the performance or economy. In addition, greater utility and convenience is achieved by the subject invention.
The product and technology disclosed comprises or consists of a novel new media and a water treatment product specifically designed to utilize and take advantages of the characteristics inherent with the media further described in this disclosure. The product described achieves high levels of water treatment efficiently, fills rapidly, and permits the total volume of the container to be filled and utilized. Clean, fresh tasting water may be delivered within sixty seconds of filling. Typically within five minutes after filling, water is delivered with=90% of lead, chlorine, and certain other contaminants removed. This is accomplished with the development of a new treatment concept combining static treatment with a water feed reservoir. To operate at optimum efficiency it is desirable to use a configuration design that basically controls the length of time the water is in contact with the treatment media. While there are several ways to accomplish this the configurations disclosed use a water in-feed orifice, or tube, which under the available head pressure allows the amount of water entering the treatment unit, or filter, to equal the void volume contained therein. By directing the in-feed water to the point furthest from the out feed, or pouring port, maximum treatment is achieved within the residence time limit designed into the product.
To achieve static treatment, activated carbon, as well as other media, are affixed to randomly oriented fibers, or other highly porous and compressible substrates. Examples of static treatment media are disclosed in my prior European Patent Application Publication number 0 402 661, the disclosure of which is incorporated herein by this reference. In accordance with the invention, the resulting matrix is compressed to form a treatment zone whereby the contaminant molecules contained within the treatment zone are within 1.5 millimeters, or less of a carbon, or other media element. Such a configuration provides for the movement of contaminant molecules to an active site on the media within a practical amount of time, without requiring convective flow. Diffusivities of common water contaminants are on the order of 5xc3x9710xe2x88x926 cm2/s, allowing treatment of the water within a time span of seconds to minutes, even without water flowing through the filter. Diffusion and equilibrium within a body of fluid are well known phenomena, which form the basics of the mechanism by which static treatment functions. Static treatment requires the body of water being filtered to be placed within the treatment media and left in contact for a specific period of time. The time element for contact is generally from 30 seconds to 10 minutes depending upon the contamination and removal percentage required. As an indicator of the validity of the concept, one may model the diffusion of a well-mixed solution poured into a static treatment device as a plane source of contaminant between two planes of adsorbent. If the diffusivity is assumed to remain constant, the amount of contaminant which has traveled the distance to the adsorbent planes can be readily calculated. While an actual estimation of the degree of removal with time depends on the concentration profiles employed, these calculations illustrate the general nature of solute migration within the low-density medium.
The equation for diffusion in one dimension when the diffusivity (D) is constant is written             ∂      C              ∂      t        =      D    ⁢          xe2x80x83        ⁢                            ∂          2                ⁢        C                    ∂                  x          2                    
Differentiation of this diffusion equation results in a solution for the concentration profile   C  =            A              t        2              ⁢          xe2x80x83        ⁢          exp      ⁡              (                                            -                              x                2                                      /            4                    ⁢          Dt                )            
where A is an arbitrary constant. This solution is symmetrical with respect to x=0 and approaches zero as x approaches positive or negative infinity for time  greater than 0. For a reference cylinder of infinite length and unit cross sectional area, the total amount of substance diffusing (M) is given by   M  =            ∫              -        ∞            ∞        ⁢          C      ⁢              xe2x80x83            ⁢              ⅆ        x            
If we rewrite the equation for the concentration distribution given above so that
xe2x80x83x2/4Dt="xgr"2, dx=2(Dt)0.5d"xgr"
we see that the amount of substance diffusing remains constant and equal to the amount originally deposited on the plane at t=0 and x=0.   M  =            2      ⁢              AD        0.5            ⁢                        ∫                      -            ∞                    ∞                ⁢                              exp            ⁡                          (                              -                                  ξ                  2                                            )                                ⁢                      xe2x80x83                    ⁢                      ⅆ            ξ                                =          2      ⁢                        A          ⁡                      (                          π              ⁢                              xe2x80x83                            ⁢              D                        )                          0.5            
Substituting for A in the equation for the concentration distribution yields   C  =            M              2        ⁢                              (                          π              ⁢                              xe2x80x83                            ⁢              Dt                        )                    0.5                      ⁢          xe2x80x83        ⁢          exp      ⁡              (                                            -                              x                2                                      /            4                    ⁢          Dt                )            
or alternatively       C    /    M    =            1              2        ⁢                              (                          π              ⁢                              xe2x80x83                            ⁢              Dt                        )                    0.5                      ⁢          xe2x80x83        ⁢          exp      ⁡              (                                            -                              x                2                                      /            4                    ⁢          Dt                )            
The following table describes the relationship between the percentage of starting material which has diffused to the adsorptive sites (C/M), the distance between adjacent adsorptive particles (assuming the plane of initial contamination was equidistant between them), and the time required for this diffusion to take place.
Generally speaking, with static treatment, no water flow takes place during the treatment process. In contrast dynamic filtration, which is used in all current consumer products, has the water flowing through the filtration media. This provides a shortened time in contact unless the water is trickled through slowly, thus requiring an inordinate period of time to deliver water in a non-pressurized system, or an impracticably large filter.
The rate of contaminant removal in porous materials is controlled by two principle mechanisms: mass transfer-resistances and the kinetics of adsorption/desorption. In filtration using activated carbon (and most other adsorbents), the kinetics of adsorption/desorption are very rapid compared to the rate of mass transfer between the bulk fluid and the solid. Hence the overall rate of contaminant removal is determined primarily by the mass transfer resistances of the system. These resistances are normally characterized as resulting from external film mass transfer resistance and intraparticle diffusion within the pores of the solid. A discussion of the intricacies of intraparticle diffusion is not germane to the teachings of this invention, in that they apply to all methods of water filtration using porous adsorbents. External film resistance to mass transfer describes a laminar sublayer of solvent (water as described in this example) through which mass transfer only takes place by molecular diffusion. The inner surface of the boundary layer is occluded by the surface of the adsorbent particles, allowing access to the inner adsorptive sites at only the pore openings. In traditional filtration the thickness of this layer is very small, and controlled by the velocity of fluid flowing past the adsorbent surface. In flow systems the principle mass transfer resistance is generally intraparticle diffusion, since the boundary layer is small as is the area accessible to molecular diffusion.
In contrast, for a static system, the boundary layer is very pronounced. At its limiting case, the boundary layer extends all the way between adjacent adsorbent particles. As the effects of bulk molecular diffusion on mass transfer are enhanced by the thickness of the boundary layer, the role of this resistance (rather than on intraparticle diffusion) on controlling the overall rate of contaminant removal becomes more predominant. Thus in a static treatment system, the control of operational performance shifts from the physical nature of the adsorbent to the manner in which the adsorbent is deployed.
There are several important implications to transferring control in this manner. The distance between adsorbent particles may now be expanded up to a point, where the rate of contaminant removal is optimized with regard to the size of the treatment device and its capacity to contain a fluid to be treated. The restriction of maintaining an adsorbent bed density at a certain level to promote effective hydrodynamic operation is no longer a concern. The device is no longer designed to provide flow under conditions where the depth of the boundary layer is minimized, eliminating criteria which make it difficult to design a small device which performs at a high level as defined by consumer demands. Summarizing the mechanism of static treatment, contaminant molecules contained within an extended boundary layer of solvent surrounding the treatment media, are adsorbed and removed from primarily the water contained within the pores of the adsorbent particles. As molecular contaminants are removed from the local environment of the adsorbent pores, other molecules enter this environment through diffusion at a rate that is dependent upon their diffusivity and concentration. Thus, the process is a continuing one where contaminants are continuously being stripped from the localized water within the micropores of the treatment media and replaced by a constantly reduced contaminant level, until the contaminant level in the bulk fluid approaches the local equilibrium concentration within the micropores. Should the carafe or water container be left with the water undisturbed, thermodynamic forces will allow contaminant molecules to reach and bind to the adsorbent. If disturbed convection currents will enhance the action.
The extraparticle/extrafiber porosity of the treatment matrix may be closely controlled to optimize the functions of (1) Filling or replenishing, (2) Time in contact required to achieve contaminant results and, (3) Rate of pouring, or flow of treated water from the treatment media. Functions (1) and (3) are most easily achieved with a more open, less restrictive filter density. Function (2), contact time required is reduced as the density is increased.
The BET surface area (Journal of the American Chemical Society, vol. 60, p309, 1938) of a particular adsorbent is often used to reflect the number of binding sites available for contaminant removal per unit mass, and the ratio of pore volume to this surface area as an indicator of adsorption preferences based on molecular size of the contaminant. The porosity (pore volume per unit mass) of an adsorbent has also been used to provide an indication of adsorptive capacity. However, fluid contained within the pore structure of the adsorbent media is not generally accessible for removal from the filter, as capillary forces tend to hold it in place. Thus the overall porosity of the medium is not a useful descriptor of the treatment capacity of an adsorbent bed used in static treatment.
The only fluid (in particular water) which is available for use from any filtration device is that which is contained in the extra-particular or xe2x80x98bulkxe2x80x99 volume surrounding the adsorbent. In static treatment, this bulk volume must be sufficient to deliver a useful amount of fluid from the filter when drained, yet the distance between adsorbent particles must be small enough for the bulk fluid to approach equilibrium within a practical time.
A useful term to describe a filter medium, which can be operated in a static manner, is the ratio of xe2x80x9creadily deliverable fluid volumexe2x80x9d (RDV) to bed volume (BV). Readily deliverable fluid volume is defined here as the volume of fluid, which will drain from a decanted filter bed without the application of any external force (other than gravity). Static filters typically have an RDV from about 30 to 60 percent of the BV.
Traditional filtration devices cannot be operated effectively in a static manner, because the extra-particular bulk volume in a packed bed is very small relative to the bed volume. The RDV of a granular activated carbon bed packed with 12xc3x9740-mesh carbon is typically 5 percent of the BV when measured with a bed diameter/depth ratio greater than one. The utilizable volume is even smaller under conditions of actual use. The argument cannot be made that a packed bed overlaid with a column of fluid constitutes static treatment, as the mean distance between a fluid molecule and an adsorptive site is too large to allow for treatment within a reasonable amount of time. In addition, in such a system the tortuocity of the fluid path between the particles of the packed bed would hinder diffusion to the point of making the majority of the bed inaccessible to adsorption.
Density is achieved by compressing an open matrix to reduce the average distance between adsorbent particles, or individual void which holds the water, to be approximately 65 nL (or 65xc3x9710xe2x88x928 liters) in volume. This equates to a RDV/BV ratio in the neighborhood of 0.4. Larger voids are tolerated if residence time between use is not a priority.
Total effective treatment area is a function of the mass of the adsorbent contained in the treatment matrix. The composition of the static treatment media must be optimized to provide for a matrix with sufficient structural stability so as not to migrate during use, as well as containing enough adsorbent to effect a useful capacity for chemical removal. A preferred embodiment of media is disclosed in Appendix A hereto. A matrix of sufficient rigidity to be compressible, yet not pack when wet is created by using a 480 oz./cubic yd. non-woven polyester substrate coated with a mixture of activated carbon (and/or ion-exchange, zeolite compounds or other treatment media) and binder at a level of 50-200% by weight. Other substrate densities which are known to be effective include non-woven polyesters with densities ranging from 480 to 720 oz./cubic yd., however much lower densities are applicable if steps are taken to support the media during hydrodynamic conditions. The substrate used is not restricted to polyesters, only to materials which are appropriate to the desired end-use. For filters designed for use in treating potable water, a substrate which is listed under Title 21 of the Code of Federal Regulations, Section 177.2260 (21 CFR xc2xa7177.2260, the disclosure of which is hereby incorporated by reference herein and a copy of Appendix B hereto) is appropriate. Certain types of cellulose pulp, cotton, nylon, rayon and polyethylene terephthalate are described in 21 CFR xc2xa7177.2260. For other applications, such as decontamination of a non-potable liquid waste stream, a substrate with different properties may be more appropriate. The adsorbent material used to coat the substrate is typically ground to a powder in order to facilitate the coating process and improve the kinetics of adsorption, but static treatment media can be produced using particles of essentially any size so long as the RDV/BV requirements are not violated. An alternative but less flexible media form is to produce a porous monolithic element comprising or consisting of one or more treatment medias typically bound together with a polymer. Such a treatment element differs from treatment elements typically known as xe2x80x9cCarbon Blockxe2x80x9d filters as a result of the greater porosity required. The porosity allows the volume of water treated to be useful and function as a static filter as previously disclosed. Such porosity greatly limits the ability of the element to function in a dynamic treatment mode.
When a substrate is used to support the carbon or other treatment media, the media must be bound to the substrate. While there are a number of methods that may be employed, dipping, spraying, and vacuum deposition for example, an important element is the chemical-bonding agent used. Not only must the largest number of contact sites be left available for contaminant removal, but the bonding chemical must also be appropriate to the intended end-use conditions. For example, media which is intended for use in treating potable water should contain binders which are listed in 21 CFR xc2xa7177.2260. Research has indicated that certain acrylics are one of a few bonding agents which meet all of the physical as well as toxicological requirements for this application. A wider variety of binders, including vinyl chloride polymers, may be appropriate to other applications.
To be attractive to the consumer, the filtration pitcher or carafe of the invention must fill rapidly, be able to filter a prescribed volume of water within 30 seconds for taste, and 2-10 minutes for optimal removal of the targeted contaminants, generally lead and chlorine. The filtration element should be easily replaceable and, to the degree possible unobtrusive. The filter must be sized and configured to treat water efficiently yet not to retain an excessive quantity of water. In a product design employing static filtration a filtration element positioned at the base of the pitcher, or container, best serves this criteria. A container filled with the media would retain too much water as a result of surface adhesion. To gain residence time in a static mode not only is the filter positioned at the base of the container, but the water path, or entry, into the filter element is through ports positioned at the back, or handle, end. Thus, when poured, the water within the filter is retained and precluded from going back into the reservoir during the pouring cycle, yet free to exit for pouring from the container. The rear entry of the water into the filter delivered to the base also provides the longest water path through the filter to the forward exit opining in the filter at the pouring end of the pitcher.
The second element in this product design is the unique carafe or pitcher, which facilitates embodiment of a static treatment filter. The pitcher comprises or consists of a compartmentalized container, which is essentially made up of a main body, which is separated into a raw water containing section and a pouring section. The containing section is integrated with the pouring section substantially only at the base of the pitcher, at the points of engagement with the treatment element. The treatment element occupies the base area of the pitcher and extends some 1.5 inches to 3 inches up from the base, but may be more or less. The treatment element has a water access opening to the rear of the pitcher and the second opening at the front end of the treatment or filter housing. Water from the filter element enters the pouring chamber of the pitcher through the chamber access hole. A seal is formed between the raw water containing component and the filter. Some designs may also require a seal with the pouring chamber. The treatment element is replaceable. The pitcher container has another unique feature, a closed top in the form of a horizontal baffle, or sealing top. An access port is built into the top for filling the container with water, or the entire top cover may be removed.
The advantage of placing the treatment element at the base of the pitcher is that standing in the up-right position water enters the filter and remains within the treatment element until poured out. The filter is sized to accommodate typically 2-3 eight ounces of water per pour. When the contents of the filter element have been poured out, the filter rapidly refills through the fill port positioned at the back, or handle, side of the pitcher. Fill of the treatment element is rapid from the water remaining within the raw water reservoir. The pitcher may be poured immediately, delivering good tasting water, or more highly treated water by waiting 2-5 minutes.
According to one aspect of the present invention a water filtration assembly is provided comprising the following components: A first housing defining a raw water reservoir and having upper and lower end portions. A raw water inlet opening defined in the upper end portion of the first housing to allow raw water to flow therethrough into the raw water reservoir. A closure structure operatively connected to the upper end portion for selectively closing the inlet opening of the first housing. A filter housing having a raw water inlet port in operative communication with the raw water reservoir for receiving raw water from the lower portion of the first housing, and an outlet port for filtered water. And a treatment media disposed in the filter housing for treating water flowing from the raw water reservoir into the filter housing through the inlet port.
Typically, the assembly further comprises a conduit for conducting raw water from the inlet port of the filter housing to a portion of the filter housing remote from the inlet port. In one embodiment of the invention the first housing comprises an inner, substantially liquid impermeable housing, the inner housing being disposed in an outer, substantially liquid impermeable housing having upper and lower end portions, a radial gap being defined between at least a portion of the inner and outer housings so as to define a pour chamber, the pour chamber being in sole communication with the outlet port of the filter housing for receiving filtered water therefrom. For example, the closure structure comprises a semi-fixed portion, a hinged portion for being moved between open and closed positions selectively providing access to the raw water inlet opening, and a pour chamber cover hingedly coupled to the semi-fixed portion for movement between open and closed positions selectively permitting dispensing of filtered/treated water from the pour chamber. The filter housing may be disposed in said lower end portion of said inner housing and an outlet port is defined in a side wall of said inner housing for being aligned with said outlet port of said filter housing.
The inner container may be selectively removable from the outer container, and the filter housing may be seated in the lower end portion of the outer housing. The filter housing may be laterally displaceable relative to the first housing, and a pour spout may be provided for selective flow communication with the outlet port of the filter housing.
The assembly may further comprise first and second ribs provided on an inner wall of the first housing for defining a pour spout section for receiving the pour spout housing, the pour spout housing having a bottom inlet opening and a top outlet opening.
In another embodiment, the first housing comprises a substantially liquid impermeable housing having bottom and side walls, a filter housing receiving section being defined in the first housing, adjacent the raw water reservoir, the filter housing being selectively axially displaceable into and out of the filter housing receiving region. The assembly may further comprise first and second rib elements in the first housing for defining the filter housing receiving region. The inlet port of the filter housing may be defined in a bottom end wall thereof and the outlet defined at an upper end thereof. A check valve may be provided for selectively closing the inlet port of the filter housing, and a spacer component may be provided for spacing the bottom end wall of the filter housing from the bottom wall of the first housing. The spacer may comprise a spring element which urges the filter housing upwardly relative to the bottom wall of the first housing.
The closure structure may comprise a semi-fixed portion and a hinge portion movable between open and closed positions selectively providing access to the raw water inlet opening.
The treatment media may comprise a composite structure of carbon and a polyester substrate carrier in one of sponge and fiber form, compressed to form a treatment zone whereby contaminate molecules suspended in water contained in the treatment zone are within about 1.5 mm of the carbon. The filter housing may occupy about 20% of the volume of the first housing. The treatment media may further comprise a static treatment media, the filter housing holds between about 16 and 24 ounces of water, and the treatment media removes at least about 70 to 90% of chlorine and at least about 90% of lead present in the raw water within about 1 to 5 minutes of filling of the filter housing. Typically, the chlorine and lead are removed within about 1-2 minutes of initial filling.
According to another aspect of the present invention a filtration medium is provided comprising randomly oriented inert fibers in mat form with a bulk density of about 200-600 grams per cubic yard of a nominal {fraction (1/16)} to xc2xd inch thickness, one of bonded and coated with a treatment media comprising at least one of activated carbon, zeolite compounds, ion-exchange resins, iodinated resins, and contaminate specific polymers, the treatment media ranging from about 100 grams per square yard to 300 grams per square yard, and compressed to obtain a certain void size distribution, as discussed in Appendix A.
According to yet another aspect of the present invention a method of purifying the water using a water filtration assembly including a first housing having upper and lower end portions and defining a reservoir for water to be purified, and a filter housing having a treatment media disposed therewithin, an inlet port for receiving water from a lower end portion of the reservoir, and an outlet for purified water. The method comprises: (a) Flowing water to be purified into the reservoir through an opening defined in the upper end portion of the first housing, at least some of the water to be purified flowing from the lower end portion of the reservoir through the inlet port into the filter housing. (b) Maintaining the water to be purified in the filter housing for at least about 30 seconds in contact with the filter media disposed therewithin, to effect removal of contaminants therefrom. And (c) dispensing through the outlet port water that has been purified in and exited the filter housing.
Typically (b) is practiced to fully treat the water to be purified to remove at least about 70% of the chlorine and at least about 90% of the lead in the water to be purified, to produce purified water, in about 1-2 minutes.
The method may further comprise placing the filter housing in the first housing, so that the filter housing is seated adjacent a bottom wall thereof. The method may also further comprise moving the filter housing laterally relative to the first housing and into operative communication with the lower end portion of the raw water reservoir. The method may still further comprise inserting the housing into the filter housing receiving compartment, and/or inserting a pour housing into the first housing and placing the pour housing in flow communication with the outlet port of the filter housing.
The above and other objects, features, and characteristics of the present invention as well as the methods of operation and functions of the related elements of the structure, and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following description and the appended claims.